Chev 350 fuel consumption

[Gordon]

Thanks for your posts Dano and Bed 767.

Dano, I was interested to hear that you are running a Holley 350 on your lwb. I'd be keen to hear what your consumption works out to.

Like yours, my motor is stock standard. Its really just a cruiser and I have no plans to modify the engine in any way. Since I do pretty high mileage in the van I'd be happy to sacrifice some grunt for improved fuel consumption. I'm running electric cooling fans and a standard mechanical water pump. Also running a mechanical power steering pump.

My current exhaust system isn't the best. It runs 2.5 inch diameter pipes from the block hugger extractors that blend into a single 3 inch pipe just before the silencer box and then a 3 inch single outlet from the silencer. I have been told that a complete dual system with a balance pipe would provide better breathing, so that is on my "to do" list for sometime in the future.

Air filter is the common aftermarket round jobbie with a K&N filter. No additional cooling ducting though.

[MaTTe]

Gordon, firstly, that is horrible fuel consumption.

Is your quickfuel a vac sec, or double pumper? If double pumper that is your cause.

For a little bit of insight, I have a 350 chev in my van, and have always run quadrajets, I modify them to suit my needs.

My best mate recently bought a valiant regal coop with a built 318 v8 in it., it came supplied with a 600 holley vac sec, running like a dog. I spent 4 weeks tuning it trying to get power out of it, and when it finally made decent power, it was guzzling fuel. Much to my mates disgust, I put a quadrajet on it (he had a dual pattern manifold) and it instantly had better economy and WAY more power than the holley even at the most powerful tune I could set it up for.

There are 2 reasons for this. Small primaries give better throttle response, while only requiring to feed small bores at light throttle, much better for the majority of driving. Then the secondaries open up, which are significantly larger than the holley, but they only feed the amount of air the motor requires, rather than completely opening instantly and pouring unnecessary fuel down the intake manifold.

If you would like to pay shipping costs, I would be happy to send you a quadrajet to test back to back on your motor Gordon (or anyone else), it may require some adjustment depending on the demands of your motor, as i'll have it setup to run on mine, however it should be good to go out of the box.

Personally I think Holleys are only good as door stops, quick fuels give more tunability to improve the holley design, however will never be as dynamic in metering fuel flow as a quadrajet.

Just my opinion however..

I also have an iron spreadbore manifold here to suit sbc if anyone is interested, its yours for the cost of shipping.

[taggraphx]

I totally agree with you MaTTe, I had a quadrajet in my 307 van, it was cheaper to run than the modified 6 that was in it before and heaps more user friendly, and once those huge secondaries were opened it put your head into the back of the seat, never gave me any trouble, yet my friends had Holleys and always seemed to be adjusting and fiddling with them

[Gordon]

Matte, thanks for the additional info. My existing Quickfuel has vacuum secondaries. I've read a few posts on a couple of V8 forums and there have been lots of positive comments regarding quadrajets. Only negatives that I have seen have been around the amount of time it takes to set them up. I guess you have got that taped by the sound of things.

What model quadrajet would you recommend?

[BusyKiwi]

Any carb once set up goes well.
Worn Holleys do need adjusting often, edelbrocks are good (what i use) and quad jets can be awesome if set up right, can be better for hi performance engines.
There is a guy in the states who is a quad jet guru. give him your specs of engine and drivetrain and what you want to do
(ie race) and he will build you a carb to suit. A mate got one done for his '68 pontiac (getting close to 1000hp).

Gordon, if you want ideal fuel consumption then injection would be the way to go. Lots of V8's came out with it, just make sure it's the old block not the vortec block style

[Gordon]

Ta Busy, I got offered a complete factory GM TPI fuel injection system including inlet manifold, dizzy, ecu and wiring harness for a really decent price last weekend. Was the one suited to my heads too, but I'm really keen to stick with a carbie setup.... less to go wrong in my opinion. I've got a feeling that the guys who did my original tune have done something wrong. I've been recommended to another crowd and plan to visit them for a chat. Will keep you all posted.

[Postie Bob]

Here`s a carb for sale....
 https://www.facebook.com/photo.php?fbid=719648208090914&set=pcb.744979122228130&type=1&theater
Any good for you?
It`s not mine.... just spotted it while browsing  .
Cheers, Bob.

[Gordon]

Thanks for that Bob !

[MaTTe]

Bob, that looks like a fairly good condition Pontiac carby. It is a little expensive for my linking, however if it is in good condition and complete could be a worthy purchase. I would be very keen to pull it apart and survey all of the internal settings to add them to my records.

Gordon, I obviously find it easier to locate Holden carbys, however with a chev the water neck comes quite close to the fuel inlet even with a 90degree elbow. This can be made to connect up without concern using the correct parts, however a chev carby with the side inlet is obviously the preferred option over a Pontiac/oldsmobile/holden/etc front inlet carby on a chev motor.

I personally like to use the 1977 onwards late model carbys as it is quite easy to adjust the part throttle mixtures, however the pre 1974 carbys can be good too with a little dedication to getting their part throttle adjustment operational.

I have setup both old and new, front and side inlet carbys on my motor. I make internal modifications as necessary, and use a lamda sensor to gauge the differences in drivability. I have both the book by doug roe, and the book by cliff ruggles. Both of which are excellent, however I find that setting the carbys up as prescribed tend to be less effective than the methods I use myself - on my motor and mates motors anyway.

The beauty of a quadrajet, is that it can be fairly standard and still give quite good results provided it is in good condition and designed for a similar capacity to what you are using.

Does your intake manifold support dual bolt patterns? or will you require an adapter? IF you require an adapter, be careful to ensure you are not getting vacuum leaks on the base plate, as I did have a vacuum leak present with an adapter a while back which throws up a whole raft of tuning issues

[Gordon]

Thanks for the additional info Matte.

My existing manifold is a squarebore setup with mounting for a Holley/Quickfuel, so I will need to run an adapter plate if I was to go down the Quadrajet path.